ios - 在 iOS 中下载 JSON 对象时出现问题

Question

在我的 iOS 应用程序中，我使用 JSON 上传 MySQL 对象。

这是 celForRowAtIndexPath 方法:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    Lista_Actividades_TableViewCell *cell =[tableView dequeueReusableCellWithIdentifier:@"Cell"];
    if (cell ==nil){
        cell = [[Lista_Actividades_TableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:@"Cell"];
    }

    cell.dia_label.hidden = NO;
    cell.minutos_label.hidden = NO;

    cell.hora_label.hidden = NO;
    cell.mes_label.hidden = NO;
     cell.puntos_label.hidden = NO;

    NSString *hora = [[categorias objectAtIndex:indexPath.row] objectForKey:@"hora_evento"];
    NSString *minutos  = [[categorias objectAtIndex:indexPath.row] objectForKey:@"minutos_evento"];


        if ([hora isEqualToString:@"0"]){
            hora = @"00";
        }
        if ([minutos isEqualToString:@"0"]){
            minutos = @"00";



        }


    if ([ [[categorias objectAtIndex:indexPath.row] objectForKey:@"hora_evento"] isEqualToString:@"0"] && [[[categorias objectAtIndex:indexPath.row] objectForKey:@"minutos_evento"] isEqualToString:@"0"]){
        cell.hora_label.hidden = YES;
        cell.puntos_label.hidden = YES;
    }
    else
    {
        cell.hora_label.text = [[categorias objectAtIndex:indexPath.row] objectForKey:@"hora_evento"];
    }
    if ([[[categorias objectAtIndex:indexPath.row] objectForKey:@"hora_evento"] isEqualToString:@"0"] && [[[categorias objectAtIndex:indexPath.row] objectForKey:@"minutos_evento"] isEqualToString:@"0"]){
        cell.minutos_label.hidden = YES;
    }
    else
    {
        cell.minutos_label.text = minutos;
    }





    if ([ [[categorias objectAtIndex:indexPath.row] objectForKey:@"dia_evento"] isEqualToString:@"0"]){
        cell.dia_label.hidden = YES;
    }
    else
    {
         cell.dia_label.text = [[categorias objectAtIndex:indexPath.row] objectForKey:@"dia_evento"];
    }

        NSString *mes_evento = [[categorias objectAtIndex:indexPath.row] objectForKey:@"mes_evento"];
        int value = [mes_evento intValue];





    if ([ [[categorias objectAtIndex:indexPath.row] objectForKey:@"mes_evento"] isEqualToString:@"0"]){
        cell.mes_label.hidden = YES;
    }
    else
    {
        switch (value)
        {
            case 1:
                cell.mes_label.text =@"ENERO";
                break;
            case 2:
                cell.mes_label.text =@"FEBRERO";
                break;
            case 3:
                cell.mes_label.text =@"MARZO";
                break;
            case 4:
                cell.mes_label.text =@"ABRIL";
                break;
            case 5:
                cell.mes_label.text =@"MAYO";
                break;
            case 6:
                cell.mes_label.text =@"JUNIO";
                break;
            case 7:
                cell.mes_label.text =@"JULIO";
                break;
            case 8:
                cell.mes_label.text =@"AGOSTO";
                break;
            case 9:
                cell.mes_label.text =@"SEPTIEMBRE";
                break;
            case 10:
                cell.mes_label.text =@"OCTUBRE";
                break;
            case 11:
                cell.mes_label.text =@"NOVIEMBRE";
                break;
            case 12:
                cell.mes_label.text =@"DICIEMBRE";
                break;
            default:
                cell.mes_label.text =@"SIN MES";
                break;
        }
    }







     cell.titulo_label.text = [[[categorias objectAtIndex:indexPath.row] objectForKey:@"titulo_evento"] uppercaseString];

    NSString *lugar = [[categorias objectAtIndex:indexPath.row] objectForKey:@"lugar_evento"];
    if ([lugar isEqualToString:@"0"]){
        NSLog(@"LUGAR AQUI ES=%@",lugar);
        cell.lugar_label.text = @" ";
    }
    else {
    cell.lugar_label.text = [[categorias objectAtIndex:indexPath.row] objectForKey:@"lugar_evento"];
    }

    NSMutableString *logo = [[NSMutableString alloc]initWithString:@"hidden here"];
    NSString *imageURL = [[categorias objectAtIndex:indexPath.row] objectForKey:@"imagen_evento"];






    if(imageURL != nil && ![imageURL isEqual:[NSNull null]])
    {
        [logo appendString:imageURL];
        NSURL *logoURL = [NSURL URLWithString:logo];
        NSData *logoData = [NSData dataWithContentsOfURL:logoURL];

        cell.imagen_label.image = [UIImage imageWithData:logoData];
    }
    else{
        cell.imagen_label.image = [UIImage imageNamed:@"no_image-512.png"];
    }





    return cell;
}

有 45 个对象，并且总是在同一个对象处，应用程序崩溃并出现以下错误:

URL = ACTteatro.jpg
mujergrancanaria(4031,0x4f9e1d4) malloc: *** mach_vm_map(size=8388608) failed (error code=3)
*** error: can't allocate region securely
*** set a breakpoint in malloc_error_break to debug
mujergrancanaria(4031,0x4f9e1d4) malloc: *** mach_vm_map(size=8388608) failed (error code=3)
*** error: can't allocate region securely
*** set a breakpoint in malloc_error_break to debug
libc++abi.dylib: terminating with uncaught exception of type std::bad_alloc: std::bad_alloc

我开发过下载更多 JSON 对象、图片和文本的应用程序，但从未遇到过此问题。

欢迎任何帮助。

Answer 1

在后台任务中下载你的图片，在主线程中进行网络操作会导致严重的问题:

要在后台任务中下载图片，您可以这样做:

if(imageURL != nil && ![imageURL isEqual:[NSNull null]])
{
    [logo appendString:imageURL];
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
        NSURL *logoURL = [NSURL URLWithString:logo];
        NSData *logoData = [NSData dataWithContentsOfURL:logoURL];
        dispatch_async(dispatch_get_main_queue(), ^{
            if (logoData.length) {
                cell.imagen_label.image = [UIImage imageWithData:logoData];
            }else{
                cell.imagen_label.image = [UIImage imageNamed:@"no_image-512.png"];
            }
        });
    });
}

希望这有助于...:)